Telescopic sight

“ We see, then, that one very important use of the telescope is to bring objects into view which otherwise we would never see; for, as I have already said, though we bring the stars into sight, we cannot magnify them. But whenever an object is near enough for the rays to fall even at a very small perceptible angle on the object-glass, then we can magnify them; and the longer the telescope, and the stronger the eye-piece, the more the object is magnified. ”

“ Yet when we come to consider what it really is which is described as being seen, when we calmly examine the various drawings which have been made by the aid of one or the other of these great telescopes, then we find that they show nothing which can not be distinctly seen and drawn by the smallest astronomical telescope of high excellence. An enormous blaze of light is gathered by the telescopes, but all this light reveals nothing which can not be seen with far greater ease in a far smaller telescope. ”

“ We have now reached the point beyond which mere telescopic power will not carry us, a point as definite for the largest instrument as for the smallest. We have traced what can be seen on the visible sun, but beyond the familiar disc, and invisible at ordinary seasons or with purely telescopic means, there lie several solar features of the utmost interest and beauty, the study of which very considerably modifies our conception of the structure of our system's ruler. ”

“ In consequence of the thinness of the rings they completely disappear from the range of vision of small telescopes when, as occurs once in every fifteen years, they are seen exactly edgewise from the earth. In a telescope powerful enough to reveal them when in that situation they resemble a thin, glowing needle run through the ball of the planet. ”

“ There is a great charm in watching this pair of stars even with a three-inch telescope—not so much on account of what is seen, although they are very beautiful, as on account of what we know they are doing. It is no slight thing to behold two distant stars obeying the law that makes a stone fall to the ground and compels the earth to swing round the sun. ”

“ To form any adequate idea of the discomfort and even danger attending the nights spent in observing, it is necessary to realise that the great telescopes used were erected in the open air, that for both the Newtonian and Herschelian forms of reflectors the observer has to be near the upper end of the telescope, and therefore at a considerable height above the ground. ”

“ But it is surely a tribute to the power and perfection of our telescopes that we have been able to discover the existence of objects so minute and inconspicuous, situated at a distance of many millions of miles, and half concealed by the glaring light of the planet close around which they revolve. ”

“ The eye-pieces to which 343 we have now adverted, when adapted to refracting telescopes, both reverse and invert the object, and therefore are not calculated for showing terrestrial objects in their natural position. But as the heavenly bodies are of a spherical form, this circumstance detracts nothing from their utility. When the celestial object, however, is at a high altitude, the observer is obliged to place his head in a very inconvenient position, and to direct his eye nearly upwards; in which position he cannot remain long at ease, or observe with a steady eye. ”

“ The angular motion of the secondary round the primary is now rapidly increasing, and the distance between the components is rapidly diminishing, so that in a few years a powerful telescope will be required to separate the pair. ”

“ It is true that we can never see them, but it is impossible to believe that space is utterly void and empty where it lies beyond the view of our telescopes. Are we to say that inside this circle stars, worlds, nebulæ, and clusters are crowded, and that outside there is nothing? Everything teaches us that this is not so. We occasionally gain accession to our power by adding perhaps an inch to the diameter of our object-glass, or by erecting a telescope in an improved situation on a lofty mountain peak, or by procuring a photographic plate of increased sensibility. ”

“ The undulations of the air, owing to the causes alluded to above, constitute one of the principal reasons why a telescope magnifying above a hundred times can seldom be used with any good effect in viewing terrestrial objects—though I have sometimes used a power of nearly 200 with considerable distinctness, in the stillness of a summer or autumnal evening, when the rays of the declining sun strongly illuminated distant objects. ”

“ Why the Planets appear dimmer when viewed thro’ telescopes than by the bare eye. 170. The more a telescope magnifies the disks of the Moon and Planets, they appear so much dimmer than to the bare eye; because the telescope cannot magnify the quantity of light, as it does the surface; and, by spreading the same quantity of light over a surface so much larger than the naked eye beheld, just so much dimmer must it appear when viewed by a telescope than by the bare eye.
Fig. VIII.
Refraction of the rays of light. ”

“ It appears to have been almost overlooked by opticians and others, that telescopes may be constructed so as to exhibit a beautiful and minute view of very near objects, and to produce even a microscopic effect, without the least alteration in the arrangement of the lenses of which they are composed. This object is effected simply by making the eye-tube of a telescope of such a length as to be capable of being drawn out 12 or 13 inches beyond the point of distinct vision for distant objects. ”

“ But as the image formed by the speculum in the aerial telescope is viewed directly, without being exposed to any subsequent reflection, it is not so liable to the tremors which are so frequently experienced in other reflectors. Notwithstanding the length of the arm of the 4 feet telescope above mentioned, a celestial object appears remarkably steady, when passing across the field of view, especially when it is at a moderate degree of altitude; and it is easily kept in the field by a gentle motion applied to the arm of the instrument. ”

“ From the images of the brighter stars rays of light project in straight lines, but these also are instrumental phenomena, due to diffraction of light by the steel bars that support the small mirror in the tube of reflecting telescopes. In a word, the stars are so remote that the largest and most perfect telescopes show them only as extremely minute needle-points of light, without any trace of their true disks. ”

“ This is managed, as in the sextant, by means of the screw, which raises or lowers the telescope. When the telescope is brought nearer to the plane of the instrument, the reflected horizon becomes dark and distinct, but when screwed off it becomes fainter, and is not so well defined. Practice alone can teach the degree of intensity which is most favourable. In general it is best to have one horizon dark, and the other light ”

“ We have deemed it expedient to introduce the above remarks on the apparent magnitude of objects, because the principal use of a telescope is to increase the angle of vision, or to represent objects under a larger angle than that under which they appear to the naked eye, so as to render the view of distant objects more distinct, and to exhibit to the organ of vision those objects which would otherwise be invisible. ”

“ It is by no means unlikely, that persons accustomed to reflection, and imbued with a certain degree of curiosity, when handling spectacle-glasses, and amusing themselves with their magnifying powers and other properties, might sometimes hit upon the construction of a telescope; as it only requires two lenses of different focal distances to be held at a certain distance from each other, in order to show distant objects magnified. Nay, even one lens, of a long focal distance, is sufficient to constitute a telescope of a moderate magnifying power, as I shall show in the sequel. ”

“ Long Telescopes may cause Objects to appear brighter and larger than short ones can do, but they cannot be so formed as to take away that confusion of the Rays which arises from the Tremors of the Atmosphere. The only Remedy is a most serene and quiet Air, such as may perhaps be found on the tops of the highest Mountains above the grosser Clouds. ”

“ Where there is an observatory and a telescope, we expect that any eyes will see new worlds at once. ”

“ He got a good glass for six hundred dollars.
His new job gave him leisure for star-gazing.
Often he bid me come and have a look
Up the brass barrel, velvet black inside,
At a star quaking in the other end.
I recollect a night of broken clouds
And underfoot snow melted down to ice,
And melting further in the wind to mud.
Bradford and I had out the telescope.
We spread our two legs as we spread its three,
Pointed our thoughts the way we pointed it,
And standing at our leisure till the day broke,
Said some of the best things we ever said. [19]
That telescope was christened the Star-splitter,
30 Because it didn’t do a thing but split ”

“ At first it had been an almost telescopic speck; it had brightened to the dimensions of the greatest star in the heavens; it had still grown, hour by hour, in its incredibly swift, its noiseless and inevitable rush upon our earth, until it had equaled and surpassed the moon. Now it was the most splendid thing this sky of earth has ever held. I have never seen a photograph that gave a proper idea of it. Never at any time did it assume the conventional tailed outline, comets are supposed to have. ”

“ V GREAT TELESCOPES AND THEIR WORK One hardly knows where, in the history of science, to look for an important movement that had its effective start in so pure and simple an accident as that which led to the building of the great Washington telescope, and went on to the discovery of the satellites of Mars. ”

“ Ever he would wander, selfcompelled, to the extreme limit of his cometary orbit, beyond the fixed stars and variable suns and telescopic planets, astronomical waifs and strays, to the extreme boundary of space, passing from land to land, among peoples, amid events. ”

“ What now, dear reader, shall we make out of our telescope? Shall we make a Mercury's magic-wand to cross the liquid ether with, and, like Lucian, [10] lead a colony to the uninhabited evening star, allured by the sweetness of the place? ”

“ By the aid of a telescope any one may behold this in a manner which so distinctly appeals to the senses that all the disputes which have tormented philosophers through so many ages are exploded at once by the irrefragable evidence of our eyes, and we are freed from wordy disputes upon this subject, for the Galaxy is nothing else but a mass of innumerable stars planted together in clusters. ”

“ Cavendish Laboratory, Cambridge, 19th March, 1879 Sir, I have received with much pleasure the table of the satellites of Jupiter which you have been so kind as to send me, and I am encouraged by your interest in the Jovial system to ask you if you have made any special study of the apparent retardation of the eclipses as affected by the geocentric position of Jupiter.
I am told that observations of this kind have been somewhat put out of fashion by other methods of determining quantities related to the velocity of light, but they afford the only method, so far as I know, of getting any estimate of the direction and magnitude of the velocity of the sun with respect to the luminiferous medium. ”

“ You are adorable, Mademoiselle. I study your feet with the microscope and your soul with the telescope.” ”

“ As Attraction is stronger in small Magnets than in great ones in proportion to their Bulk, and Gravity is greater in the Surfaces of small Planets than in [Pg 352] those of great ones in proportion to their bulk, and small Bodies are agitated much more by electric attraction than great ones; so the smallness of the Rays of Light may contribute very much to the power of the Agent by which they are refracted. ”

“ But woe is me! the longest date
Too narrow is to calculate
These empty hopes: never shall I
Be so much blest as to descry
A glimpse of thee, till that day come
Which shall the earth to cinders doom,
And a fierce fever must calcine
The body of this world—like thine,
My little world! That fit of fire
Once off, our bodies shall aspire
To our souls' bliss: then we shall rise
And view ourselves with clearer eyes
In that calm region where no night
Can hide us from each other's sight.
Meantime thou hast her, earth: much good
May my harm do thee! ”

“ Again, it is a most beautiful and delightful sight to behold the body of the Moon, which is distant from us nearly sixty semi-diameters [4] of the Earth, as near as if it was at a distance of only two of the same measures; ”

“ Astronomy teaches the correct use of the sun and the planets. These may be put on a frame of little sticks and turned round. This causes the tides. Those at the ends of the sticks are enormously far away. From time to time a diligent searching of the sticks reveals new planets. The orbit of a planet is the distance the stick goes round in going round. Astronomy is intensely interesting; it should be done at night, in a high tower in Spitzbergen. This is to avoid the astronomy being interrupted. ”

“ Nevertheless, thus clad, I trod interstellar space, exalted by the knowledge that I was bound on vast adventure, where, at the end, I would find all the cosmic formulae and have made clear to me the ultimate secret of the universe. In my hand I carried a long glass wand. It was borne in upon me that with the tip of this wand I must touch each star in passing. And I knew, in all absoluteness, that did I but miss one star I should be precipitated into some unplummeted abyss of unthinkable and eternal punishment and guilt. ”